Vehicle and elastic suspension device therefor.



R. LIBBAU. VEHICLE AND ELASTIG SUSPENSION DEVICE THEREFOR.

APPLICATION FILED DEO. 22, 1908.

Patented sepn.29,1914.

WIM/55555 W^RIOHA`BDLIEBAU, F WATERVLIET, NEW YORIQASSIGNOR TO THE WESTINGHOUSE l AIR SPRING COMPANY, A CORPORATION OF PENNSYLVANIA.

VEHICLE AND ELAs'rIc SUSPENSION DEVICE rnnnnron.

Specification of Letters Patent.

Application led December 22, 1908. Serial No. 488,762.

Patented Sept. 29, 1914.

operate satisfactorily day in and day out To all 'whom t mai/lconcern Be it known that I, RICHARD LmaAU, a

"citizen of they United States, and a resident of Watervliet, vin the-county of Albany and VState of New York, have invented certain new and useful Improvements Relating to Vehicles and Elastic Suspension Devices Tlierefor, of which the following` is a specification.

My present invention includes means whereby the load bearing platform of a vehicle may be elastically supported on its running gear, though many of the features are broadly applicable in any other relation where two bodies are so associated that resilient relativel movement vis desirable, and especially where one or the other of the y bodies is subject to sudden movements, vibrations, orl shocks, which it is undesirable to have transmitted to the other .of said bodies.

Though capable of use in other relations,v

the invention has been devised'primarily in connection with automobiles, and the general object in view has been to embody the principles of resilient support by an elastic compression medium, such as air or gas, in

' al practical, self-contained, gas-tight comrpression device adapted to serve all'of the purposes of the steel springs commonly employed, and to combine therewith all of the desirable features of a shock absorber, the

entire device being adapted to meet the exacting conditions and stand the rough usage required in connection with automobiles, de` livery wagons, trucks, railway rolling stock, etc. To this end the air compression member is'preferably so constructed and so combined with the vehicle body and running gear, that it acts solely as a compression memben the traction and other fore and aft stresses and also the lateral stresses being v'sustained by comparatively rigid supple` mental guiding members.

The elastic compression device is preferably constructed so as to operate on an unchanging body of initially supplied compressed air, thus rendering unnecessary any permanent connection with compressed air freservoirs, pumps, or other auxiliary pres` sure maintaining means. To this end, my

invention includes various features whereby the lpacking of the movable parts, as well as i the joints and metal walls of the container,

arefree from leakage, so that the device will without special care, and, in practice, requn'es no attention otherthan the usual annual or seasonal overhaulings required for such vehicles.

It has been my purpose to make the elastic c ompresslon device as short .as practicable, for a given vertical play or elastic throw, and at the same time to keep its diameter small. For ready application to existing types of automobiles, without reorganization of the construction, the diameter of the compression device ought not to be much greater than the width of the leaf' springs commonly employed in such constructions.

In order to get the required elastic throw, compression space, and clearance in a small space, I prefer to make the compression members in the form of telesc'oping tubes, with the smaller or piston tube uppermost, and terminating at the top in a compression chamber of greater diameter, preferably of a diameter equal to or greater than the maximum over all diameter found at any other portion of the length of the device. A suitable controller for the flow of fluid to and from the compression chamberV is arranged d near the upper end of the piston cylinder. The entire length of the device is thus made available as a container for the compression fluids.

A suliicient quantity of liquid is charged into the device, to bring the liquid up to or just above the level of the piston packing. The compression chamber is proportioned with respect to the total effective compression space and to the amount of liquid, so that the ratio of extreme compression is not much greater than 2 to 1 or 3 to l, though for special purposes the amount of liquid may be increased to increase the maximum ratio of compression. I prefer, however, to adjust the supporting power of the compres` sion device by increasing or diminishing the initial internal pressure of the air or other gas supplied thereto and to keep the ratio of compression about that described.

The device for controlling the flow of the compressible medium between the variable cylinder space and the fixed volume compression chamber, is preferably a valve permitting relatively free iow into the chamber and automatically throttling the reverse liow to a desired extent. As disclosed herein, the said valve has some throttling effect possible'- velocity o compression of the device, but the throttling of outflow from the compression chamber is made very -much greater for the purpose of very materially retarding the resllient upward throw of the piston after extreme compression. In all cases, I prefer to have'the proportions such that the asymmetric valve for controlling the fluid flow will operate upon the compresvsible part of the fluid medium and in actual operation will not be reached by an incompressible body of the liquid.y 1

For my purposes, I prefer to have the primary packing at the sliding joint nor` mally -submerged in a freely bathing body of liquid and to have-the valve above that level. Hence, I prefer to arrange the larger compression cylinder asfthe lowermost member and to arrange the packing upon the lower end of 'the piston cylinder sliding therein. The enlarged lcompression chamber is arranged at the uppper end of the piston cylinder, so that the foam of the liquid, which may work into said chamber in operation of the device, will drain back into the main body of the liquid in the' cylinder space.

The sliding joint between the cylinders may be made air ti ht by Amaking the packing in the form o a knife edge of elastic metalexpanded into contact with the cylinder by the internal pressure, after the manner-set forth in my prior applications Serial Nos. 411,893 and 411,894. Such a joint will hold indefinitely without leaking, provided the cylinder be made perfectly true circumferentially and of perfectly uniform diameter from end to end, and, provided the knife edge and slidingv contact surface on the pis" ton be ground to t perfectly. While lI may use this form of piston packing, I prefer to use a soft flexible cup packing, having its free edge maintained in contact with the walls of the cylinder by a rigid, resiliently forced, expanding device. Such a packing conforms perfectly to minor irregularities of contour and diameter of the cylinder, and hence neither the cylinder nor the piston need be finished with great accuracy, by which I mean that accuracy of the order of a thousandth of an inch or less is sufficient. Asa cup packing sufficiently soft and flexible and at the same time sufficiently durable for my purposes, I prefer a pressed leather cup. This material is notoriously too porous 'to perfectly hold high pressure for long periods, but I have discovered that graphite, if suiciently finely divided and suspended in the liquid within the cylinder, will be forced into the fiber of the leather, thereby completely and perfectly plugging allthe 'pores thereof.

The liquid'J-in which the lgraphite is sus- ,wall by maintaining a sealing vilmvof 'lo and *within my compression vcylinder isfprefer pendedsh'ould be-sulciently fluid for prl r flow .and draina ein cold weather,lan is selected with reference -to the-material lof' the packing with a view to keepin thematerial soft and flexible. Internalrictional I resistance of the liquid 'is unobjectionable, insomuch as'it merely affords .a vsubstitute for part of the dash-pot retardation 'which is always provided for in the device, `and frictional wear is small in any event, because bymy invention the device is relieved of all side thrust. Frictional heat," fhow ever, must be avoided, as the leather hardens and crumbles under a very moderate heat, even when amply su plied with moistenin fluid. Various liqui s, such as glycerin, o' etc., will answer the purpose, however, especially Where a freely bathing body p thereof s continuously maintained in .contact with the leather, though I prefer a nonvolatile, non-drying mineral oil, not easily oxidizable when in contact with air. t My experience is that where a liquid `is used .in y bathing contact with leather or fibervindurated or vulcanized bypmeans of any of the known chemical fillers, the liquid under enormous pressure will ultimately displace or chemically change` the filler or the maf terial of the packing, so that it becomes porous' and that only a mechanical filler, such as very finely ground graphite, talc, or similar material, suspended in the bath liquid, so as to be continually forced vinto the material by the internal pressure, can be. relied on to maintain practically perfect the texture and the tightnessof the material of the packing. The bathing liquid must be continuously copiously supplied to the packing in connection with any such mechanical filler, and this isl best accomplished from an internal supply. Another advantage of the l finely powdered filler, such as graphite, with Y a liquid, such as mineral oil, is that the liquid carries the graphite throughout the entire interior of the device, so that ,the filler is mechanically driven bythe great pressure into the pores or leaks in the material of the metal walls and into all joints of the device, as well as into the packing. For these reasons, I prefer soft, ilegible packing, such as leather, submerged 1n a liquid, such as oil, to increase and"ma 11v1." tain its iexibility', together with a mechanical filler, such as finely pulverized graphite,

to ll the pores. Both the oil and the graph`- 12e ite serve to lubricate the device sufliciently to prevent excessive wear of the leather. orV p leakage between the leather and the cylinder@ graphite therebetween. .c y

v Though the incompressible liquldlmed ably not Water, and though the compress ble gaseous medium need not be a1r,thejd vice. may be roughly `and perhaps not-Lin .of piston packing and expander; Fig. 3 is a transverse sectional view of Fig. 2; and Fi 4 is a fragmental sectional view correspon ing to Fig. `1, showin a modified form of the piston packing an expander. The compression device comprises a lower cylinder 71 closed by cap 72, provided with the lspherical bearing. The other member comprises a smaller cylinder 73 telescoping within and forming a hollow piston for cylinder 71. At the lower end of the cylinder 73 is formed a cylindrical enlargement 74, which accuratelyiits the walls of cylinder 71 'and to that extent corresponds' to a piston head. The lower end of said enlargement 74 is formed so as to afford a curved seat 75 for a cup-washer 76, which is clamped' against said seat-by an annular lip 77 of a bushing 78, screw threaded Within the cylinder 7 3. As explained above, the cup washer is preferably of compressed leather. The free edge of this washer should be cut. very smooth and is preferably beveled v just enough to form a fair seat for the expander. An important feature o'f my invention consists of an expander 79, beveled as at 80, engaging the washer near the free edge thereof and continuously forced into wedging relation with said edge by suitable means, such as a spring 81 secured at one end to a cross barV 82 on the expander 79 and at the other end to a cross bar 83, at the upper end of the bushing 78. In the upper end of the cylinder 71 is accurately fitted a split bushing 85, which affords a bearing surface for the outside of cylinder 73 and also-.an abutment for the piston head 74 to limit outward or expansive movement thereof. The bushing 85 is held in position by an annular ca-p 86, screwed over the end of -cylinder 71.

The upper end of the cylinder 73 carries the enlarged compression chamberl 90, which has an outside opening provided with a suit- `lable closure 91.

The latter Ais preferably constructed after the manner of approved types of air valves for automobile tires, so as to permit pumping up ofthe inner air pressure to any desireddegree and to insure secure closure against leakage. At the top of the cylinder 7 3, between it and the compression chamber 90, is arranged a check valve 92, provided with al stem 93 guided in bearing 94 andl held against seat 95 by means of spring 96. IThis valve is varranged so as to ail'ordv a certain definite amount of leakage in the reverse direction when the valve is closed,- and for this purpose I prefer to form an opening 97 in the valve itself. In the sideof the casting 90 is arranged a passage 100, closed by -a plug 101, through which passage'. oil may be charged into the lower part y/of the device beneath the check valve 92.

An external cylinder 105 is screw threaded at 106 to casting 90 and extends down over .the joint between cylinders 73 and 71. At

the llower end of cylinder 105, is secured an annular collar 107, bearing upon cylinder 71. Collar 107 is formed with an annular chamber 108 loosely packed, preferably with fibrous material 109. This external cylinder 105 serves as a guard to prevent access of dust or mud to the outer wall of cylinder 73, where 1t might be carried by movement of said cylinder into the cylinder 71 and thus come in contact with the piston packing 7 6 and so produce wear or leakage. The packing 109 may be itself substantially air tight, so that the volume of air contained Within 105 does not change, and if there is any leakage back and forth during operation of the device, 109 acts as a perfect filter to prevent access of anything but pure air within this space.

By enlarging the horizontal Section'of the compression chamber, the length of the de- Vice for a given compression space is decreased by thirty to fifty per cent. Making the larger cylinder 7l lowermost and filling the device with liquid to a point above the packing, affords a large body of cooling, lubricating liquid always in contact with the packing. The liquid is continuously churned about by the movable piston, thereby maintaining the graphite in suspension and circulation. The leather packing being always beneath the liquid, is thereby maintained soft and flexible. If by any chance the liquid should leak enough to fall below the normal position of the packing. this will do no harm while running, because the remaining liquid being churned into foam, will be increased in volume so as to rise in 'the piston cylinder 73. Whennot running and with a bad leak, the liquid might settle below the leather packing, and in such case, if the vehicle remained out of use for a considerable time, thereby drying the packing sufficiently to permit leak, the upper cylinder will settle to a point where the packing will again be bathed by the liquid.

The check valve for controlling the recoil of the spring is located well above the normal level of the liquid, and ifv at the start an incompressible body of the liquid does lreachsaid valve, it will be churned into foam, thus acquiring the characteristics of a compressible medium. The foaming carries the graphite into all crevices of the device. The washer cannot leak so long as maintained flexible by the liquid and impervious by the combined liquid-.and1

graphite. .A n important factor in this result is the solid wedging expander resiliently maintained .in wedgin'g.. that it ali'ords a solid backing or the-free edge of the washer. The proportion. .of parts and the angle of beveling ofthe expander are determined with reference-to the texture and. resilience ofthe leather, so

-that the extreme free edge of the packing is always in vtightest engagement with the walls of the cylinder, but as will be evident from the drawing, the angle of the cone sur-` l specific engaging surfaces employed, under the specific conditions established therebetween. For example, if the expander has adjusted itself for a given internal diameter of the compression cylinder at one point in the stroke, and it happens thatby reason of Wear or imperfection of manufacture, the diameter of the cylinder is slightly less at some other point in the stroke, the tendency to increase of the peripheral or external pressure when such point ofthe stroke is approached, will wedge the expander downwardly thereby preventing undue squeezing of the free edge of the packing ring, with the result that the upward 'and outward pressure on the cylindrical portion of the packing ring is automatically maintained practically constant in4 direction and amount notwithstanding slight variations of internal diameter. A similar automatic adjustment or self-accommodation operates to maintain uniform pressure upon the packing notwithstanding the :alternating effects of the sliding friction biatween the packing and the wall of the compression cylinder, during the alternate compression and expansion movements of the device. Upon thecompression movement this friction tends to compress and shortenl the cylindrical portion of the cup leather andv to curl the free edge thereof outwardly into desirable intimacy 'of contact with the wall of the compression vcylinder but uponthe expansion movement the friction tends to stretch and lengthen the cylindrical portion of the cup leather and to cause the free edge toacurl :away from the cylinder wall. The latter action would tend to decreasethe perfection of it and-intimacy of contact of the cylindrical portion. of the. cup leather, yet

the constant upward pressure 'of the spring ltends to maintain the relative position of the expander with respect to the cup leather osition j so ltion and intimate contact of the uppermost during such expansion movement and thereby to oppose and prevent development ofthe above mentioned f tendencyl -i to longitudinal stretching of vthe'cylindrical portion of the cup leather and curling away of the free edge thereof, during the-expansion. movements of the device. Under each and all l ofl ythese conditions of operation the action of the expanderfapplied `primarily at the edge'of the. cup leathertakes effect more VVor 75 less upwardly as well as outwardly sothat the entire exterior surface of the cylindrical portion of the cup leather as well as the free edge thereof ris maintained in most intimate sliding contact with the .adjacent wall'rof the 'compression cylinder. The norv mally continuous high pressure of the confined air within the device contributes materially to maintaining the -expanded condiportion of the cylindrical wall of the packing, at the points more remote -from the direct action of the expander, but the latter contributes, inthe manner above'- described, by reason of the upward or longitudinal. component of its wedging action and also 'by reason of the solid yet self-adjusting 'radial backing which itafords atthe -free ledge of the cup leather, therebypreventing any-imperfection of engagement and any escape of air at the edge.

It will be'. evident t0. those skilledv in the art that the herein described practicalperfection of it of the packing during the expansion movements is 4not necessary and does not exist -in the case of air or water pumps, fluid motors, or other devices in which the supply of fluid is renewed from time to time, usually during the expansion stroke of the piston,.and in which it is not necessary to maintain a normally continuous high pressure atl all times, by preventing any and practically allescape of Huid during both the expansion and compression movements of the device.

The compression throw may become very considerable, but in such case the dash-pot -action of the liquid flowing through the.

smaller cylinder 73 and the constrictions at eitherend thereof, becomes reater because of its increased velocity, an this serves to keep down excessive violence-of a compression stroke. The expansion s'trokeor rebound is subject to a much .greater retardation by reason of the closure of the check valve, which permits reverse flow of the compresed air from the compression chamber only through the hole '.in the valve and the leaks around the valve seat.V By reason of this model of operation, the wheels are1125 forced intoallslight depressions of the road without much movement of the load carryingplatform, and projections of the road fcause a slightly throttled but nearly free compression movement of the 'wheels to'- 130' from such compression being completely tempered and controlled by the check valve.

Figs. 2, 3, and 4 show modified means for rcsiliently forcing the expander into contact with the edge of the cup leather. In Figs.r 2 and. a tension rod 11.0, provided with a' flange 111 for compressing spring 112; against expander 79, is screw threaded into. the bridge 112 acrossv .the upper end of bushing 78. The forcing effect of the spring will vary according to the extent to which the rod 11() is screwed up. another variation wherein a long spring 120 is employed having a thrust bearing upon the underside of the expander 79 at one end and upon the bottom of the cylinder 71 at the other end.

In the operation of my hydro-pneumatic compression device, the 'rigid backing afforded by the expander and the resilient forcing thereof by the spring, serve to maintain the free edge of the cup packing con-l tinuously in intimate contact with the walls of the cylinder.

vice is that if the tight, the edge must not curl away from the walls of the cylinder in the least degree, and that the internal pressure can be relied upon to maintain such necessary condition of the extreme edge only by the exercise of exceptional precautions, as,

cations, the construction and vfit must be as accurate as possible. By the use of my eX- pander designed to work on the elastic edge of the packing, much less accuracy is necessary.

I prefer tol make the cylinder and the compression chamber of a material, such as fine quality bronze, the

cylinder being usually made from the bestl quality of seamless tubing and the compression chamber being of fine quality casting, preferably internally strengthened by vertical ribs, as at 90a. The interior of the casting is carefully cleaned to free it from all traces of sand and detachable fragments of metal. It is then tinned internally to insure cleanliness and filling of pores and cavities in the metal. If not tinned, or if. the tinning is imperfect, the graphite may usually be relied upon to close the .pores after the device has been in use a short time. The tubes are preferably finished internally with fine emery paper working lengthwise to insure uniformityof diameter. The rinciple joints, such as closures at andp 72, are made tight by heating and dipping the parts .in solder and screwing home while the solder is plastic. The liquid vis carefully ltered to remove all solidimpurities and the graphite is pure Fig. el shows I My experience with. pack-- ing under the conditions found in my de-j joint is to be absolutely for instance, in the case of the metallic cup of my prior appli` dense, non-'porous treme fineness The bushing 85 which .the principal metallic wear-'surface of the cylinders, is preferably made of cast iron or 4steel when the piston `cylinder 73 lis of bronze, or of bronze when said cylinder ,is of 70 cast iron or steel. The internalpress'ure is preferably high, but for convenience in practical operation of an automobile, is

' preferably not higher than can be supplied by an eiicient tire pump of the-ordinary commercial type, that is to say, some where about 150 to 200 pounds per square inch;A I find that my piston packing holds'much better for such pressures than it does forprese \sures of 40 to 60 pounds per square inch.

` With a lower cylinder 71, say two inches in diameter, thekhigher pressures will. ,sustain a load of 500 or 600 pounds per cylinder and in operation the maximum pressure may rise to two or three times the initialV pressure, so that the maximum total sustaining 'power of each cylinder may amount to 1000 to 2000 pounds steady pressure,-and` for instantaneous pressures, the dash-pot action may be relied upon to sustain consid:Y erable overload at all stages ofcompression.

It will be noted that with the proportion of parts shown in the drawing, the hollow piston has an effective area equal to the difference between the internal area` of cylin- 95 der 7l and that of cylinder 73. In the ar. rangement shown, these areas are about "as 3%; to 1, so that the amount of fluiddisplaced I by downward; movement of the .hollow piston 73 per inch of compression stroke islgo equal to the volume of about 2% inches of, the length of cylinder 73.. This volume is required to pass through the relative con.. stricted4 opening through the expander 79,; and is thus subject to a certain .amount 015.1105 modifying dash-pot action. `This relation ofy displacement areas, volumes, and constricy tion of passages results in a most desirable tempering of movements at all stages of-op-l eration, including the relatively short throw-fvno oscillations caused by small inequalities 4of-y the road which are insuiiicient to bring the check valve into full and controlling operation. l

When mineral oil is used as the liquid in-115 conjunction with air as the compressible mei dium under such high pressure, there is at first some sort of molecular or chemi'caljabsorption 'of the air by the liquid, but it ,will be understood that any initialfall of presfjrigo sure which may be noted in first operation. of the device is due to this cause, and that such action will not persist after 4the rst .y repumpin'g. v v .A

While I have herein fully shown and described, and have pointed out in the ap# y pended claims certain novel features of construction, arrangement, and operation which 4 characterize my invention,t will be underand ground to uniform eX- stoodvby those skilled in the art that vari- ,13o

- ousomissions, substitutions, andy changes in vthe forms, proportions, sizes, and details of the device'and of its operation, may be made 'without departing from the spirit of` my in- Y"vention,

.I claiin: 1.. A hydro -pneumatic supporting or I cushioning device 'comprising telescopic the cylindrical wall of the other member,

withl the free edge of the said cupped ring extending in the direction of the high gaseous pressure, anda cone expander cooperating with saidl gaseous pressure, being yieldingly forced at practically constant pressure against` Asaid free edge of said n ing the expansion movemeni cupped rin uniformly and continuously throughout its entire circumference whereby the action of the cone is se, -adjusting and Vsubstantially uniform both during the compression vmovement when the sliding friction `between the packin and v ill tends to compress and shorten t e cup irather, and durhen such friction tends to stretch and lengthen said cup leather and to curl the free edge thereof away from the cylindrical wall.

2. A hydro-pneumaticA supporting or cushioning device com rising telescopic members slidable one wit in the other and conninga body of gaseous fluid, and havingA a sliding joint provided between said niembersand comprising a cupped packing ring ,formed from a single piece of leather :clamped to'one of the members and arranged Fin extended sliding engagement with the cylindrical wall of the other member, with the free edge of the said cupped ring extending in the direction of the high gaseous pressure, a solid rigid coneV expander and yielding `means forcing said cone into en-l gagement withV the free edge of said cup; leather' in a direction parallel with the axis' of1` the device, said cone being yieldingly. fforced at practically constant pressure against said free edge of said packing uniformlyand continuously throughout its enltirey circumference whereby the action of the cone isself-adjusting and substantially unif form both during the compression movement Vthe sliding friction between the packcushioning device comprising telescopic members slidable one within the other and confining a body of gaseous fluid, and having a sliding joint provided between said members and comprising a packing-ring formed from a single` piece of leather clamped to one of the members and arranged in extended sliding engagement with theY cylindrical wall of the other member,.with the free edge of the said cupped ring extending in the direction of the high gaseous pressure, and a cone expander yieldingly forced at practically constant pressure against said free edge of said cupped ring uniformly and continuously throughout its entire circumference whereby the action of the cone is self-adjusting and substantially uniform both durin the compression movement when the sliding friction between the packing and wall tends to compress and shorten the cup leather, and during the expansion movement when such friction tends to stretch and lengthen said cup leather and to curl the free edge thereof away from the cylindrical wall, said cone expander having a wedging. angle greater than the angle of friction of its sur aces of engagement with the leather packing.

4. A cushioning device comprising telescopic members slidable one Within the other and confining a body of gaseous iuid, a packing for the sliding joint between said members, comprising a flexible cupped packing ring clamped to one of said members and arranged in extended sliding engagement with the cylindrical wall of the other member, and a cone expander yieldingly held against the free edge of the cupped ring, said cone expander having a wedging angle greater than the angle of friction of its surfaces of engagement with the leather pack- -igned at New York city, in the county of New York and State of New York, this fourteenth day of December,` A. D. 1908.

RICHARD LIEBAU.

Witnesses: y

'GEORGE C. DEAN, IRVING M. OBRIEGHT. 

